1. Keystroke-Level Model IST 331 Gaurav Dubey Based on ‘The ABCs of Users’, Ritter et al 2011

2. Keystroke-level model Simplified version of GOMS Fast, approximate way to calculate time taken to complete a task Assumptions – Simple world – Single-tasking – No interruptions – Single method to complete a task

3. Characteristics No need to worry about goals or selection rules Easier to use, but more limited applicability Can be improved by incorporating Fitts’ Law, and by using tables for keystroke speeds for individual keys

4. Operators Keystrokes (K): 0.08s to 1.2s per keystroke, mouse click, or button press Pointing (P): 1.1s (or as determined using Fitts' Law) for moving mouse to target Homing (H(mouse) or H(keyboard)): 0.4s for moving hand between mouse and keyboard Drawing (D): 0.9n + 0.16l where n = number of segments, l = total length of segments

5. Operators Mental operators (M): 1.35s to think about task – These should be placed between all operators EXCEPT those linked through knowledge or skill (essentially, they should be placed between complete "cognitive units") System response time (Sys): as estimated based on system